I was trying to connect to S3 today, and both Transmit and Forklift were giving me connection errors:

PLAIN TEXT
XML:
  1. <Error>
  2.     <Code>RequestTimeTooSkewed</Code>
  3.     <Message>The difference between the request time and the current time is too large.</Message>
  4.     <MaxAllowedSkewMilliseconds>900000</MaxAllowedSkewMilliseconds>
  5.     <RequestId>68532E845A05B015</RequestId>
  6.     <HostId>FfoBOO+7Kh+0Aa35f+Oa0P+Beeym+10LNyLVTGI3VgEHkVjotak8+L1QHaWOsIaf</HostId>
  7.     <RequestTime>Fri, 22 Jan 2010 00:10:57 GMT</RequestTime>
  8.     <ServerTime>2010-01-21T23:53:58Z</ServerTime>
  9. </Error>

The problem: my system clock was manually set 15 minutes fast. The s3 api will check the request time against the time on the server to see if it's been too long, and if it has, it returns the above error. Fixing the time solved it.